Internal validity - is there true cause and effect between variables.
内部有效性——在条件变化的时候，其成因和结果还会是真实的么？
2
The algorithm is two-order convergent, Whose validity is confirmed by effect of the image separation test.
该算法具有二阶收敛性，其有效性为文中展示的图像分离测试效果所证实。
3
Through to the analysis of the simulation test in the lab and the test data in the field, the authors discussed TDR monitoring landslide practical application effect and validity.